Roller shades generally use a long loop of beaded cord (called a roller chain) as part of the shade control mechanism. The roller chain is coupled to a control unit which engages the roller tube upon which the blind is rolled. Pulling on the roller chain causes the control unit to rotate the roller tube so as to raise or lower the blind as required. Since the control unit is mounted at the top of the blind, the chain must be sufficiently long to be easily accessible to the user. This results in a long loop of chain which hangs down from the control unit. In order to prevent a child from accidentally choking on the loop of roller chain, a tensioner is provided for securing the bottom end of the chain against a wall or window frame.
The tensioner is often mounted inside the window frame such that the loop of roller chain hangs down with both lines parallel. It is important to keep the lines of the roller chain parallel. If the lines of the roller chain cross, then there is an increased chance that the roller control mechanism might jam. If the tensioner is to be mounted outside the window frame (such as against a wall adjacent the window opening) then a special adapter bracket is generally required to orient the tensioner such that the lines of the roller chain remain parallel and do not cross. In order to minimize the complexity of the assembly of the blind, and to provide a clean look, a universal tensioner is required which permits for inside or outside mounting without causing the lines of the roller chain to cross.